Variability of mitochondrial DNA mutagenesis in human blood

Abstract

The 4977 bp deletion of mitochondrial DNA (mtDNA) is known to accumulate with age in postmitotic tissue. Meanwhile, this mutation can also be detected in tissues with a fast turnover: blood or skin. However, in those tissues there seem to be several factors influencing mtDNA mutagenesis additionally to the age of an individual, e.g. specific drugs, cigarette smoke or alcohol. From a forensic point of view the question arose whether mt mutagenesis in blood might be used as an indicator to estimate the age of an individual. We investigated mtDNA mutagenesis in blood from 10 persons (22–60 years) over a time period of 6 months. Specific habits of the participants such as smoking, alcohol consumption or intake of medicine were also monitored. Every 2 weeks a blood sample was taken and the following parameters were analysed: (1) amount of total mtDNA/cell and (2) the occurrence of 4977 bp deleted mtDNA (dmtDNA). Real time PCR results showed values between 1003 and 3275 mtDNA copies/cell with a very strong variation within one individual from time point to time point. Using Duplex-PCR, the occurrence of dmtDNA also varied considerably, showing dmtDNA/mtDNA ratios from 0 to 1.7 in the same individual only at different days with no correlation to age or gender. Taken together, the 4977 bp deletion of mtDNA in blood is not suited in a forensic approach to estimate the age of an individual.